The invention relates to vehicle axle suspension systems of the type that have beam assemblies constructed of several individual pieces, which are rigidly attached together, in order to form an integral structure. Such structures of this type generally allow substantially all forces or deflections that are experienced by the axle to be transmitted to a frame connection member. An axle which carries ground-engaging wheels is secured to the beam assembly, and an air bag or similar system is disposed in load-transmitting relation between the assembly and the vehicle frames, at the end of the beam opposite a pivot connection. This invention relates to certain unique beam assemblies and axle connections to the beam, and force transferral means in association therewith.
It is known, in beam-type suspension systems, to make use of a system including a vehicle frame, a hanger bracket, a beam, an axle seat, and an air spring, to transfer the forces experienced by the ground-engaging wheels through the axle seat to the beam, and thereafter into the appropriate frame member of the vehicle. In each of these cases, a connection has been used between the axle and the beam, with the intention of transferring those forces to the beam in a safe and efficient manner. Not all have been successful in this regard.
Exemplary of such prior art vehicle suspension systems achieving a modicum of success in this regard are U.S. Pat. Nos. 4,615,539 to Pierce; 2,879,076 to Stricker, Jr.; and 4,261,597 and 4,566,719, both to VanDenberg. The Pierce and Stricker, Jr. patents disclose a vehicle suspension system in which the forces experienced by the ground-engaging wheels are transferred from the axle to the beam by means of gusset plates or, alternatively, axle seats. While these systems have met with a degree of commercial success, they are made up, of necessity, of numerous parts. The shear number of these parts and their complex arrangement, are necessary to properly transfer many of the forces from the axle to the suspension beam while allowing adequate and appropriate deflections so that damage to the axle and suspension beam do not occur. Some of the forces, resulting from deflections caused by uneven road surfaces, are distributed throughout the gusset plates or axle seat, and result in various distributed and concentrated loading into the suspension beam components. In addition, the number and size of the parts involved add significant weight to the suspension. The absorbing of a significant amount of deflections experienced in a high stress situation, by any part, including the gusset plate and axle seat, other than the elastic bushing at the pivot in the hanger leading to the frame member, is undesirable. A more advantageous system which would be the desireable low stress situation would be presented if the forces were not absorbed by the gusset plates or axle seats. Consequently, if not individually highly stressed, the gusset plates or axle seats transmit the forces required to control the vehicle attitude to the suspension beams. Therefore, the axle seat is not overstressed when transmitting forces between axle and beam.
In the VanDenberg patents ('597) and ('719), extra elements are employed to secure the beam to the axle, usually by welding to the axle, in order to provide the necessary attachment means for the axle seat. While these systems are highly advantageous, these extra elements add weight and cost to the suspension system, and, therefore, reduce the maximum permissible load that can be carried in jurisdictions where that weight is limited. They do, however, provide an acceptable long-lived means of transferring forces from axle to beam. Nevertheless, the transferring of forces between axle and beam in these systems still requires an intermediary component, such as an axle seat.
It is apparent from the above that there exists a need in the art for a suspension system which is lightweight, due to the number and simplicity of its component parts and its unique structure, and which at least equals the performance characteristics of the known suspensions, such as those of the highly advantageous type disclosed in the above-referenced VanDenberg patents. It is also desirable to provide a structure, as described above, which at the same time transmits substantially all of the deflections from the relatively rigid, axle-beam structure during the vehicle roll, walk or articulation to the resilient pivotal connection to the hanger bracket, rather than imposing deflections in the gusset plates, axle seats, or the like. It is a purpose of this invention to fulfill these and other needs in the art in a manner more apparent to the skilled artisan once given the following disclosure.